Various degenerative conditions, such as osteoarthritis and dysplasia, can affect the function of the elbow. Surgical treatment either to repair or replace the joint is necessary to avoid the joint becoming useless.
Replacement elbow joints for dogs have already been proposed.
US Patent Application Publication No. 2004-220675 discloses a prosthetic elbow joint for a dog in which a humeral component having an elongate stem and spiral grooved cylindrical head is engaged with a corresponding spiral ridge on an ulnar component that is attached to the ulna. This document suggests that the grooved and ridged nature of the replacement joint provides desirable lateral stability for the joint. The ulnar component is implanted by cutting an extensive L-shaped portion out of the ulna. To prepare and implant this component requires very invasive surgery, which may disrupt ligaments and require extensive soft tissue dissection. This can lead to undesirably long recovery times.
US Patent Application Publication No. 2005-043806 proposes a less invasive canine elbow replacement technique. Here, the humeral component comprises a stem that is insertable between the medial and lateral condyles of the humerus into the medullary canal. To permit this, a trochlear portion of bone between the medial and lateral condyles is cut out. To fix the humeral component in place, a transcondylar screw is located between the medial and lateral columns of the humerus. The ulnar component defines a U-shaped cavity for cooperating with the humeral component. This component is attached to the ulna by using a jig to cut a squared portion at the proximal end of the ulna, where it is fixed using a pin down the ulna's canal and an anconeal screw. This implanting process requires the anconeal process of the ulna to be removed.